Information playback systems frequently utilize a stylus for reading signals from the surface of an information record, typically a plastic disc that contains stored video and audio information. In some systems the information record has a fine spiral groove to guide the tip of a stylus that contains a thin electrode. In these systems, the stylus tip is made of a material having sufficient hardness to withstand the abrasion caused from tracking the groove. Materials which possess such hardness, such as diamond, generally have a crystallographic structure which presents surfaces exhibiting different qualities depending upon which crystallographic plane the surfaces are oriented along. The video disc stylus utilized in the CED (capacitance electronic disc) system is tapered to form the prow of the tip, and is also lapped to form a keel having a V-shaped shoe for its bottom portion. Making a long-shanked stylus entirely from the same material may become expensive, particularly when the tip material, for example diamond, exceeds the cost of other suitable materials from which the shank can be made.
In order to reduce manufacturing costs, a metallic-shanked diamond audio stylus may be utilized as a starting structure from which to manufacture the video disc stylus. A typical audio stylus has a length of about 2.5 millimeters. The shank of the audio stylus comprises a titanium rod having a diameter of about 300 micrometers, at the end of which is mounted a randomly-oriented natural diamond stone in the shape of a 50 degree cone. In fabricating the desired structure from the diamond tip of the audio stylus, a reference surface is cut along a chord of the cylindrically-shaped metallic shank about 50 micrometers in from the circumference, in order to ensure that the proper orientation is achieved during each of the fabricating processes. The present invention provides a novel method of forming such reference flats along the cylindrical shanks of a plurality of audio styli.